Veteran Apple software designer Greg Christie, who played a major role in the development of the iPhone, will be retiring later this year, Apple confirmed after a Wednesday report by the Wall Street Journal.

The Journal report said Apple said in an internal email that Christie, who leads the company's human interface team that designs software for its products, would be retiring. Jony Ive, Apple's product design chief, recently became Christie's boss. (The team previously reported to Craig Federighi, Apple's software chief.) Ive is already warmed up for new duties in the area of software, having recently played a key role in the development of iOS 7.

Friction between Christie and Ive was at the root of Christie's decision to leave, said the Apple enthusiast site 9to5Mac, which first reported Christie's departure. But Daring Fireball reported that the alleged disputes were normal artistic differences and that indeed Christie's departure was long planned, as was Ive's expanded role. A TechCrunch report also said there was no drama in Christie's departure, and that he would continue at the company in a limited role as an Apple special projects adviser for at least several months.

Apple told the Journal that Christie had previously planned to retire later this year after 20 years of service, without commenting on reports that Christie and Ive were at odds or of a new role for Christie. "He has made vital contributions to Apple products across the board and built a world-class human interface team which has worked closely with Jony for many years," an Apple spokeswoman told the Journal.

Christie is not a household name like Steve Jobs, Apple's late CEO, or Ive, the iPhone's hardware designer. But the work Christie did on the iPhone is lasting, and his departure opens up a new avenue for Ive to handle more of the iPhone's software development.

Christie helped to develop many of the functions of the iPhone, with his name listed on the patent for the "slide to unlock" function. That patent is now one of more than a dozen at issue in Apple's lawsuit against Samsung, now being heard in a federal court in California.

Christie testified just last week in the trial, recounting the early days of the iPhone's development before it was announced in 2007. "It was nerve-racking, we all wanted it to go perfectly," he testified last week. "There was a lot of anticipation. We were hoping we were right and that people would get it."

Christie joined Apple in 1996, after software he had written for Newton Messagepad, Apple's short-lived personal digital assistant, attracted the attention of executives.